Passive or hands-free entry and start systems for motor vehicles are known, the systems allowing a user carrying an electronic key (e.g. shaped as a credit card), or another portable electronic device having the same electronic key functions to open and lock the vehicle and/or to start and stop the engine of the vehicle, without needing to carry out active operations, such as pressing a button on a remote control or inserting a mechanical key into a specific latch, or with a considerable reduction of the operations actively requested by the user.
For example, the user may at the most be asked to touch a sensitive part of a vehicle handle or to press a button coupled to the handle to indicate the intention to access the vehicle, or to press a start button inside the vehicle to express the intention to start the engine.
In particular, passive entry/passive start systems of known type for use in a motor vehicle use two different communication channels: a first low frequency radiofrequency communication channel in the LF—Low Frequency range (typically with a frequency of 125 kHz), directed from a central electronic management unit on the vehicle to the electronic key (or similar portable device) carried by the user; and a second radiofrequency communication channel operating at a high frequency (typically in the UHF—Ultra High Frequency radio frequency range, e.g. with values of 315 MHz, 434 MHz or 868 MHz), operating in the reverse direction, i.e. directed from the electronic key carried by the user to the electronic central management unit on the vehicle.
The radiofrequency communication on the first communication channel allows to locate the user carrying the electronic key near the vehicle and to recognize in detail the position respect to the access openings of the same vehicle (typically the right and left front doors and, if required, the tailgate) in order to enable opening of the corresponding locking device of the vehicle.
With this regard, it is worth noting that “locking device” hereinafter means a generic element moveable between an opening position and a locking position, adapted to open or, respectively, lock a corresponding access opening to an internal environment of the vehicle, e.g. including doors, tailgate, an electric window, a sunroof or similar elements.
In particular, known systems envisage the use of a certain number of low frequency antennas, coupled to the vehicle, outside the same vehicle, having appropriate ranges of action to allow to locate the user in required positions with respect to the vehicle. For example, such low frequency antennas are arranged at the right and left doors and at the tailgate of the vehicle.
In general, the low frequency antennas are operatively coupled to a similar antenna integrated in the electronic key so as to detect the presence thereof according to a response received following a query sent to the same electronic key.
The radiofrequency communication on the second communication channel allows to exchange authentication data (e.g. including an appropriate identification code) between the electronic key (or similar portable device) of the user and the electronic central management unit on the vehicle, in order to authenticate the key and authorize the user to enter and/or start the vehicle.
Typically, the second communication channel is activated once the user is effectively located in the neighborhood of the vehicle by means of the communication which occurred on the first communication channel.
Furthermore, passive entry/passive start systems are generally required to discriminate between the situation in which the electronic key is inside the vehicle and the situation in which the same electronic key is outside the vehicle, for example in order to: enable starting the vehicle; lock the doors automatically once the user has actually left the passenger compartment (the so-called walk-away function); avoid the possibility of accidentally leaving the electronic key inside the vehicle after the latter has been locked.
In order to implement such a further location need, known solutions use a low frequency antenna (e.g. again operating at a frequency of 125 kHz), arranged inside the passenger compartment of the vehicle.
In all cases, known systems have some drawbacks which do not allow to exploit their undoubtedly advantageous features to the full (including that of allowing a user to enter and operate a vehicle without performing active actions, besides approaching the vehicle itself and possibly touching or brushing against a respective handle or actuating a start button in the passenger compartment).
In particular, the arrangement and the installation of low frequency antennas for the operations of locating and recognizing the user, in addition to implying non-negligible operating costs and times, require complex wiring, in particular for interfacing with the electronic central management unit on the vehicle. Furthermore, rather complex operations are generally required for calibrating all the antennas.
The described systems are not free from security problems, in particular due to the possibility by persons with malicious intent to intercept the radiofrequency communications and/or use possible radio links (the so-called “two-thief attack”) to enter the vehicle to the detriment of the legitimate owner.